1. Field of the Invention
This invention relates to a process for the production of 2-alkyl- or alkenyl-2-oxazolines corresponding to general formula (I) ##STR1## in which R.sup.1 is an optionally hydroxy-, dihydroxy- or hydroxy, C.sub.1 -C.sub.2 -alkoxy-substituted hydrocarbon radical containing at least 7 and more especially 7 to 21 carbon atoms in the carbon chain, by condensation of fatty acid ethanolamides or precursors thereof in the presence of catalysts in the liquid phase.
2. Discussion of Related Art
2-Alkyl-substituted 2-oxazolines are valuable intermediate products which are used inter alia as solvents or plasticizers and, in particular, as polymerization components. Numerous processes have been described for the preparation of this class of compounds.
The most simple method comprises the cyclodehydration of N-2-hydroxyethyl carboxylic acid amides (Chem. Rev. 44, 447 et seq. (1949), Chem. Rev. 71, 485 et seq. (1971)). However, cyclization of the unsubstituted N-2-hydroxyethyl carboxylic acid amides requires very drastic conditions or the presence of special catalysts. Whereas reactions in the gas phase in the presence of dehydrating metal oxides, such as Al.sub.2 O.sub.3, SiO.sub.2 -Al.sub.2 O.sub.3, Al.sub.2 O.sub.3 -TiO.sub.2, TiO.sub.2 or MgO, have proven to be suitable for the production of readily volatile, short-chain 2-alkyl-2-oxazolines, the less volatile, longer-chain 2-alkyl-2-oxazolines are better produced in the liquid phase. Compounds of manganese, cobalt, molybdenum, tungsten, iron, cadmium, zinc and tin and of the rare earth metals have been described as catalysts for the liquid-phase reaction (cf. U.S. Pat. No. 3,562,263, Belgium Patent 666,829, C.A. 87, 135353, C.A. 87, 135352, U.S. Pat. No. 3,681,329, U.S. Pat. No. 3,681,333, European Patent 00 33 752, U.S. Pat. No. 4,543,414, U.S. Pat. No. 4,354,029, U.S. Pat. No. 4,443,611, European Patent 0 105 944 and European Patent 0 164 219). However, the catalysts described in the above cited publications do not lead to good yields in the preparation of relatively long-chain 2-fatty alkyl-2-oxazolines.
It has now been found that special titanium and zirconium compounds are eminently suitable as catalyst in a process of the type mentioned above with yields of up to about 90% of the theoretical, based on the starting compound, being obtainable.